Interpretive Summary: This is the first report of a pathogenic virus discovered to infect the brown citrus aphid, BrCA. Alternatives to pesticides are a growing interest to control insect pests, protect the environment, reduce groundwater contamination, and to protect beneficial insects. Research was conducted using a newly discovered iridovirus, to determine its effect on BrCA biology. The virus was shown to infect aphids through feeding and to cause an increase in adult aphid mortality. Aphids, which fed on a virus solution died earlier and had fewer nymphs than the aphids, which only fed on a sucrose solution. These results demonstrated, that the use of aphid infecting viruses needs to be further examined for use in current integrated pest management programs aimed at controlling this serious pest of citrus.

Technical Abstract:
This is the first report of a pathogenic iridovirus in the brown citrus aphids, BrCA, Toxoptera citricida (Kirkaldy), and evidence of its subsequent transovarial transmission. Aphids are important horticultural pests, which have few biological control agents, which are available for use in their management. A newly discovered Iridovirus, a dsDNA virus, with an icosahedral symmetry and ~120 nm diameter was shown to infect BrCA. Invertebrate iridescent iridoviruses are known to infect many insect groups; this is the first report of a pathogenic virus in citrus aphids. Modes of transmission for iridovirus in other insect systems have been shown to be through oral ingestion, and cuticular wounding. We demonstrated virus transmission by aphids through oral ingestion via sucrose feeding experiments, and provide the first evidence of vertical, transovarial transmission of an iridovirus, as confirmed by PCR analysis of virus-infected nymphs. Pathology observed on aphid biology: Virus fed aphids had an increase in mortality and reduced fecundity over control aphids. At 22 days post-treatment 95% of the treated aphid adults had died, while 70% of the control aphid population had died. The virus-fed aphid population reached 100% mortality 6 days earlier than the control aphid population. Virus-fed aphids had a lower fecundity rate, producing 41.25% fewer offspring than the control aphids. The exploitation of entomopathogenic viruses in aphids may aid current integrated pest management programs.